von Willebrand factor (vWf) is a large adhesive plasma glycoprotein which is instrumental in mediating the interaction of platelets with damaged endothelial surfaces. It also serves as a carrier for factor VIIIC, the antihemophilic factor, serving to increase the plasma half life VIIIC. vWf, thereby, plays a central role in the normal hemostatic process. Qualitative and quantitative deficiencies in vWf are associated with von Willebrand's disease, the most common inherited bleeding abnormality. It has been recently estimated that about 1% of the population carries an abnormal gene for vWf. The majority of the individuals have mild or inapparent disease, but some have significant bleeding problems which are often difficult to treat. vWf appears to be expressed only in endothelial cells (EC) and in megakaryocytes. In recent years, much progress has been made in studies on the structure/function relationships of plasma vWf, and on its biosynthetic processing steps in EC. Several groups; including our own, have reported the cloning of vWf cDNA from human EC libraries. In this application we propose to isolate the complete gene for vWf and to characterize its structure and its expressional control elements. We have already obtained human genomic clones spanning greater than 90 kb and corresponding to more than 2/3 of the mRNA. We will try to obtain the balance of the vWf gene and determine its detailed structure, eventually by sequencing the intron/exon boundaries. We will also attempt to determine the DNA regions which control the tissue specific expression of vWf using systems involving transient and stable expression of monitor genes regulated by sequences from the cloned vWf gene.